Failure to resolve billing issue

Hi,

I switched my package to Essential Broadband Plus on 03/02/2024, at a rolling monthly cost of £20/month. I was contacted via email in December 2024, stating that my discounted rate would expire after 12 months, and that I needed to confirm that I was still receiving Universal credit via web chat. I did this on 07/01/25, and the agent confirmed that my discounted package would continue at the same rate for another 12 months. However, by bill for February showed that I had been moved off the discount, and charged a package change fee of £5.87, with a new broadband fee of £28. I called customer support on the morning of 01/02/25, and they agreed to adjust my bill back to £20. This did not happen. I went through the web chat once again, and they again confirmed that I was now on the discounted rate of £20. I have screenshots of the web chat to prove this. However, after these 3 attempts to keep my package as it was, all of which were confirmed at the time, my bill for this month still shows £33.87. I am at my wits end here. It's like they are agreeing to resolve things, but then doing absolutely nothing. Perhaps the next stage is to lodge a complaint.